Radial pre-swirl assembly and cooling fluid metering structure for a gas turbine engine

ABSTRACT

A gas turbine engine comprises a pre-swirl structure coupled to a shaft cover structure and located radially between a supply of cooling fluid and a flow path. The pre-swirl structure defines a flow passage and includes a plurality of swirl members in the flow passage. A flow direction of cooling fluid passing through the flow passage is altered by the swirl members such that the cooling fluid has a velocity component in a direction tangential to the circumferential direction. The bypass passages provide cooling fluid into a turbine rim cavity associated with a first row vane assembly to prevent hot gas ingestion into the turbine rim cavity from a hot gas flow path associated with a turbine section of the engine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 12/758,069, (Attorney Docket No. 2010P00100US), filed Apr. 12,2010, entitled “COOLING FLUID METERING STRUCTURE IN A GAS TURBINEENGINE” by Keith D. Kimmel et al., the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to gas turbine engines, and moreparticularly, to a gas turbine engine including a radial pre-swirlassembly and a metering structure associated with a plurality of bypasspassages.

BACKGROUND OF THE INVENTION

In gas turbine engines, compressed air discharged from a compressorsection and fuel introduced from a source of fuel are mixed together andburned in a combustion section, creating combustion products defininghot working gases. The working gases are directed through a hot gas pathin a turbine section, where they expand to provide rotation of a turbinerotor. The turbine rotor may be linked to an electric generator, whereinthe rotation of the turbine rotor can be used to produce electricity inthe generator.

In view of high pressure ratios and high engine firing temperaturesimplemented in modern engines, certain components, such as rotatingblade structures within the turbine section, must be cooled with coolingfluid, such as compressor discharge air, to prevent overheating of thecomponents. The rotating components associated with the rotor may bemoving at a substantially higher speed than the cooling air supplied forcooling the components such that the cooling air may produce a dragforce on the rotating components, which may result in reduced output ofthe engine and an increased temperature of the cooling air.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a gasturbine engine is provided having a central axis defining an axialdirection. The engine comprises a supply of cooling fluid, a rotatableshaft extending in the axial direction of the engine, and shaft coverstructure disposed about the shaft such that a flow path extends in theaxial direction between the shaft and the shaft cover structure. Theengine further comprises pre-swirl structure coupled to the shaft coverstructure and located radially between the supply of cooling fluid andthe flow path, the pre-swirl structure extending in a circumferentialdirection about the shaft. The pre-swirl structure comprises forwardwall structure and aft wall structure spaced in the axial direction fromthe forward wall structure. The forward and aft wall structures define aflow passage therebetween, the flow passage including an inlet incommunication with the supply of cooling fluid and an outlet incommunication with the flow path. The flow passage supplies a firstportion of cooling fluid from the supply of cooling fluid to the flowpath. The pre-swirl structure further comprises a plurality of swirlmembers in the flow passage extending between the forward and aft wallstructures. Each swirl member includes a leading edge and a trailingedge spaced from the leading edge in a radial direction, wherein thetrailing edge is offset from the leading edge in the circumferentialdirection. A flow direction of the first portion of cooling fluidpassing through the flow passage is altered by the swirl members suchthat the first portion of cooling fluid has a velocity component in adirection tangential to the circumferential direction when the firstportion of cooling fluid enters the flow passage. The engine alsocomprises at least one bypass passage defined through the shaft coverstructure and including an exit opening at an end of the shaft coverstructure. The at least one bypass passage receives a second portion ofcooling fluid from the supply of cooling fluid and supplies the secondportion of cooling fluid to a turbine rim cavity associated with a firstrow vane assembly to prevent hot gas ingestion into the turbine rimcavity from a hot gas flow path associated with a turbine section of theengine.

In accordance with a second aspect of the present invention, a gasturbine engine is provided having a central axis defining an axialdirection. The engine comprises a supply of cooling fluid, a rotatableshaft extending in the axial direction of the engine, and shaft coverstructure disposed about the shaft such that a flow path extends in theaxial direction between the shaft and the shaft cover structure. Theengine further comprises pre-swirl structure coupled to the shaft coverstructure and located radially between the supply of cooling fluid andthe flow path, the pre-swirl structure extending in a circumferentialdirection about the shaft. The pre-swirl structure comprises a flowpassage including an inlet in communication with the supply of coolingfluid and an outlet in communication with the flow path. The flowpassage supplies a first portion of cooling fluid from the supply ofcooling fluid to the flow path. The pre-swirl structure furthercomprises a plurality of swirl members in the flow passage. The swirlmembers each include a leading edge and a trailing edge spaced from theleading edge in a radial direction, wherein the trailing edge is offsetfrom the leading edge in the circumferential direction. A flow directionof the first portion of cooling fluid passing through the flow passageis altered by the swirl members such that the first portion of coolingfluid has a velocity component in a direction tangential to thecircumferential direction when the cooling fluid enters the flowpassage. The engine also comprises a plurality of bypass passagesassociated with the shaft cover structure. The bypass passages receive asecond portion of cooling fluid from the supply of cooling fluid andsupply the second portion of cooling fluid to a turbine rim cavityassociated with a first row vane assembly to prevent hot gas ingestioninto the turbine rim cavity from a hot gas flow path associated with aturbine section of the engine. The engine still further comprises ametering structure associated with an outlet of each bypass passage. Themetering structure comprising a plurality of flow passageways formedtherein for permitting the second portion of cooling fluid in the bypasspassages to pass into the turbine rim cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a sectional view of a portion of a gas turbine engineaccording to an embodiment of the invention;

FIG. 2 is a perspective view partially in section of a portion of thegas turbine engine illustrated in FIG. 1;

FIG. 3 is a perspective view partially in section of the portion of thegas turbine engine illustrated in FIG. 2 taken from a different angle;

FIG. 4 is a cross sectional view illustrating a plurality of swirlmembers according to an embodiment of the invention;

FIG. 5 is an end view of a shaft cover structure according to anembodiment of the invention shown removed from the gas turbine engineillustrated in FIG. 1;

FIG. 6 is a diagram illustrating swirl ratios of cooling fluid passingout of a pre-swirl structure according to an embodiment of theinvention;

FIG. 7 is a sectional view of a portion of a gas turbine engineaccording to another embodiment of the invention;

FIG. 8 is a partial cross sectional view illustrating portions of ashaft cover structure and a pre-swirl structure of the gas turbineengine illustrated in FIG. 7, wherein the shaft cover structure and thepre-swirl structure have been removed from the engine for clarity; and

FIG. 8A is an enlarged view of a portion of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, specific preferred embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand that changes may be made without departing from the spirit and scopeof the present invention.

Referring now to FIG. 1, a portion of a gas turbine engine 10 accordingto an embodiment of the invention is shown. The engine 10 includes aconventional compressor section 11 for compressing air. The compressedair from the compressor section 11 is conveyed to a combustion section12, which produces hot combustion gases by burning fuel in the presenceof the compressed air from the compressor section 11. The combustiongases are conveyed through a plurality of transition ducts 12A to aturbine section 13 of the engine 10. The turbine section 13 comprisesalternating rows of rotating blades 14 and stationary vanes 18. A firstrow 14A of circumferentially spaced apart blades 14 coupled to a firstblade disc structure 114 and a first row 18A of circumferentially spacedapart vanes 18 coupled to an interior side of a main engine casing (notshown) and a first lower stator support structure 118 are illustrated inFIG. 1. A plurality of the blade disc structures, including the firstblade disc structure 114, are positioned adjacent to one another in anaxial direction so as to define a rotor 16. Each of the blade discstructures supports a plurality of circumferentially spaced apart bladesand each of a plurality of lower stator support structures support aplurality of circumferentially spaced apart vanes. The vanes 18 directthe combustion gases from the transition ducts 12A along a hot gas flowpath HG onto the blades 14 such that the combustion gases cause rotationof the blades 14, which in turn causes corresponding rotation of therotor 16.

As shown in FIG. 1, a shaft cover structure 20 surrounds a portion of ashaft 22, which shaft 22 is coupled to the rotor 16 for rotation withthe rotor 16. It is noted that the shaft cover structure 20 may bemounted to the main engine casing and does not rotate with the shaft 22and the rotor 16 during operation of the engine 10. In an embodiment,the shaft cover structure 20 may comprise two halves or sections thatare joined together about the shaft 22, such as, for example, bybolting, although it is understood that the shaft cover structure 20 maybe formed from additional or fewer pieces/sections. The shaft coverstructure 20 comprises a generally cylindrical member having a forwardend portion 24 and an opposed aft end portion 26.

Referring still to FIG. 1, the forward end portion 24 of the shaft coverstructure 20 includes a shaft seal assembly 28 that creates asubstantially fluid tight seal with the shaft 22. The shaft sealassembly 28 may comprise, for example, a rotating structure, such as aknife edge seal, coupled to the shaft 22, which may be in combinationwith a non-rotating seal structure, such as a honeycomb seal or anabradable material coupled to the forward end portion 24 of the shaftcover structure 20. Other suitable exemplary types of shaft sealassemblies 28 include leaf seals, brush seals, and non-contacting finseals.

The aft end portion 26 of the shaft cover structure 20 comprises apre-swirl structure 30 and defines a plurality of bypass passages 32 anda particle collection chamber 34, each of which will be described indetail herein.

An outer cover 40 is disposed radially outwardly from the shaft coverstructure 20. The outer cover 40 includes a forward end portion 42upstream and radially outward from the forward end portion 24 of theshaft cover structure 20 and an aft end portion 44 radially outward fromthe aft end portion 26 of the shaft cover structure 20. First sealstructure 46, such as, for example, a dog bone seal or diaphragm seal isdisposed between the forward end portion 24 of the shaft cover structure20 and the outer cover 40 for creating a substantially fluid tight sealtherebetween. Second seal structure 48 is located between the shaftcover structure 20 and the outer cover 40 adjacent to the respective aftend portions 26, 44 thereof. The second seal structure 48 creates asubstantially fluid tight seal between the aft end portion 26 of theshaft cover structure 20 and the aft end portion 44 of the outer cover40. In the embodiment shown, the second seal structure 48 also providesa structural support for the shaft cover structure 20 via the outercover 40. It is noted that the outer cover 40 is non-rotatable and isstructurally supported within the engine 10 by the main engine casingvia a plurality of struts (not shown).

A cooling fluid chamber 50 is located radially between the shaft coverstructure 20 and the outer cover 40 and axially between the first andsecond seal structures 46, 48. The cooling fluid chamber 50 receivescooling fluid from a supply of cooling fluid, e.g., compressor bleed airthat is cooled in an external cooler (not shown), from a plurality ofcooling fluid feed tubes 52 (one shown in FIG. 1). The cooling fluidfeed tubes 52 deliver the cooling fluid into the cooling fluid chamber50 through one or more respective apertures 54 formed in the outer cover40. The cooling fluid, which may have a temperature of, for example,between about 250-350° F., is used to cool the shaft cover structure 20,the shaft 22, and structure in the turbine section 13 of the engine 10,as will be described in greater detail herein.

Referring additionally to FIGS. 2 and 3, a first portion of coolingfluid supplied by the cooling fluid chamber 50 flows through a series ofpre-swirl passages 60 (one shown in FIGS. 1-3) that extend through theshaft cover structure aft end portion 26 from the cooling fluid chamber50 to an annular pre-swirl chamber 62. The first portion of coolingfluid flows from the pre-swirl passages 60 into the pre-swirl chamber 62and is provided to the pre-swirl structure 30.

As shown in FIGS. 2 and 3, the pre-swirl structure 30 includes aradially inner wall structure 64 that extends about the shaft 22 and isfixedly coupled to the shaft cover structure 20. The pre-swirl structure30 also includes a radially outer wall structure 66 radially spaced fromthe inner wall structure 64. The outer wall structure 66 extends aboutthe shaft 22 and is also fixedly coupled to the shaft cover structure20. The inner and outer wall structures 64, 66 define an annular flowpassage 68 therebetween, which flow passage 68 includes an inlet 70 andan outlet 72 (see also FIG. 4), through which the first portion ofcooling fluid passes after entering the pre-swirl structure 30 from thepre-swirl chamber 62.

A plurality of swirl members 74 extend in the flow passage 68 and spanbetween the inner and outer wall structures 64, 66. As more clearlyshown in FIG. 4, the swirl members 74 each include opposed first andsecond sidewalls 75A, 75B, a leading edge 76 at the flow passage inlet70 and a trailing edge 78 at the flow passage outlet 72. The leadingedge 76 of each of the swirl members 74 is offset from the trailing edge78 in the circumferential direction, as shown in FIG. 4. Thus, the firstportion of cooling fluid flowing through the flow passage 68 is causedto change direction by the swirl members 74, such that the first portionof cooling fluid exiting the flow passage outlet 72 has a velocityvector V (see FIG. 4) with a velocity component V^(TC) in a directiontangent to a circumferential direction, wherein the circumferentialdirection is defined by a first circumferential surface of the innerwall structure 64, and an axial velocity component V_(A) as it flowsdownstream toward the turbine section 13 of the engine 10, as will bedescribed in detail herein. An angle β between the velocity vector V andits velocity component V_(A) may be between about 65° and about 85°. Aradial height H (see FIG. 2) of each of the swirl members 74 accordingto an exemplary embodiment of the invention may be about 15-25 mm and achordal length L (see FIG. 4) of each of the swirl members 74 accordingto an exemplary embodiment of the invention may be about 60-105 mmaccording to one embodiment of the invention.

Referring to FIG. 4, in a preferred embodiment, the swirl members 74 areconfigured such that the cooling fluid exiting the flow passage outlet72 flows or moves in a direction D at an angle θ_(D) of from about 65°to about 85° relative to a central axis C_(A) (see FIGS. 1 and 4) of theengine 10. Such a flow direction D of the cooling fluid can be effectedby forming the trailing edges 78 of the swirl members 74 so that theyextend at an angle θ_(SM) of from about 65° to about 85° relative to thecentral axis C_(A) of the engine 10.

Further, the swirl members 74 in the preferred embodiment arecircumferentially spaced from one another so as to allow a desiredamount of cooling fluid through the flow passage 68 to adequately coolthe structure to be cooled in the turbine section 13 of the engine 10.As shown in FIG. 4, the narrowest spacing S_(P) between the trailingedge 78 of one swirl member 74 and an adjacent swirl member 74, whichspacing S_(P) may also be referred to as the throat section between theswirl members 74, is also preferably configured to obtain a desiredpressure drop, i.e., caused by a Venturi effect effected by theconverging sidewalls 75A and 75B of the swirl members 74, and to cause acorresponding velocity increase as the cooling fluid flows through theflow passage 68. According to one embodiment, the narrowest spacingS_(P) between the first sidewall 75A at the trailing edge 78 of oneswirl member 74 and the second sidewall 75B of the adjacent swirl member74 may be about 10 mm, but may vary depending upon the particularconfiguration of the engine 10. It is noted that the velocity componentV^(TC) of the cooling fluid exiting the flow passage outlet 72 in thedirection tangent to the circumferential direction is preferably greaterthan a velocity component of the shaft 22 and the rotor 16 in thedirection tangent to the circumferential direction during operation ofthe engine 10, as will be discussed in greater detail herein.

Since the pre-swirl structure 30 is located close to the shaft 22, aleakage interface area between the pre-swirl structure 30 and the shaftcover structure 20 is reduced, as compared to if the pre-swirl structure30 were to be located further radially outwardly. Specifically, theleakage interface area between the pre-swirl structure 30 and the shaftcover structure 20 is defined as the area between where the radiallyinner wall structure 64 and the shaft cover structure 20 meet, inaddition to the area between where the radially outer wall structure 66and the shaft cover structure 20 come together. Since these areas arelocated generally close to the shaft 22, their circumferences arerelatively small (as compared to if these areas were located radiallyoutwardly further from the shaft 22), such that the leakage areas arerelatively small. This is compared to a configuration where the leakageareas are radially outwardly further from the shaft 22, in which casethe circumferences of the leakage interface areas would be larger. Thissame concept applies for leakage through first and second sealingstructure 98 and 106, each of which will be discussed below.

An annular cavity 84 is located downstream from the pre-swirl structure30 and extends from the flow passage outlet 72 to a plurality of bores86 formed in the first blade disc structure 114. As illustrated in FIGS.1-3, the annular cavity is substantially defined by the first blade discstructure 114, the pre-swirl structure 30, and a particle deflectingstructure 90, which particle deflecting structure 90 will be describedin detail herein. The bores 86 in the first blade disc structure 114extend radially outwardly and axially downstream through the first bladedisc structure 114 to the first row 14A of blades 14 to provide thefirst portion of cooling fluid to internal cooling circuits 14A₁ formedin the blades 14, see FIG. 1.

Referring back to FIGS. 2 and 3, a particle separator 89 according to anaspect of the present invention comprises the particle deflectingstructure 90 and the particle collection chamber 34, which, as notedabove, is defined by a portion of the shaft cover structure 20. Theparticle deflecting structure 90 is located in the annular cavity 84downstream from the pre-swirl structure 30 and upstream from the bores86 in the first blade disc structure 114. The particle deflectingstructure 90 is coupled to and extends radially inwardly from a seal arm92 of the first blade disc structure 114, and, thus, rotates with thefirst blade disc structure 114 and the rotor 16 during operation of theengine 10.

The particle deflecting structure 90 includes a radially inwardlyextending portion 94 that extends radially inwardly from the seal arm 92of the first blade disc structure 114 and a generally axially extendingportion 96. The radially inwardly extending portion 94 includes aradially inner end portion 97, which end portion 97 is curved in theradial direction such that it extends in the axial direction at its endtoward the pre-swirl structure 30 and the particle collection chamber34. The end portion 97 is located further radially inwardly than theaxially extending portion 96, which axially extending portion 96 extendsgenerally axially from the radially extending portion 94 toward thepre-swirl structure 30 and the particle collection chamber 34. However,as most clearly seen in FIG. 6, the axially extending portion 96 isslightly sloped in the radial direction as it extends toward thepre-swirl structure 30 and the particle collection chamber 34, i.e., theaxially extending portion 96 is sloped such that it expandscircumferentially in a direction toward the particle collection chamber34. As will be described in detail herein, the particle deflectingstructure 90 deflects solid particles from the first portion of coolingfluid into the particle collection chamber 34 after the first portion ofcooling fluid exits the pre-swirl structure 30.

Referring to FIGS. 2 and 3, the first sealing structure 98 is locatedradially outwardly from the annular cavity 84 between the shaft coverstructure 20 and the axially extending portion 96 of the particledeflecting structure 90. The first sealing structure 98 is locatedaxially between the flow passage outlet 72 and the bores 86 in the firstblade disc structure 114. The first sealing structure 98 limits leakagebetween the annular cavity 84 and a turbine rim cavity 100, whichturbine rim cavity 100 is defined by the first blade disc structure 114and the first lower stator support structure 118 and is locatedproximate to the hot gas flow path HG. Additional details in connectionwith the turbine rim cavity 100 will be discussed in detail herein. Thefirst sealing structure 98 may comprise, for example, one or moreknife-edge seal members 102 extending radially outwardly from theaxially extending portion 96 of the particle deflecting structure 90,and a honeycomb seal or abradable material 104 associated with the shaftcover structure 20. It is noted that other types of sealing structuremay be used.

Also shown in FIGS. 2 and 3, the second sealing structure 106 isemployed between the shaft cover structure 20 and the shaft 22 proximateto the aft end portion 26 of the shaft cover structure 20. The secondsealing structure 106 limits leakage between the annular cavity 84 and ashaft cover cavity 108, which shaft cover cavity 108 will be discussedin detail herein. The second sealing structure 106 may comprise, forexample, one or more knife-edge seal members 110 extending radiallyoutwardly from the shaft 22, and a honeycomb seal or abradable material112 associated with the shaft cover structure 20. It is noted that othertypes of sealing structure may be used.

Referring still to FIGS. 2 and 3, the shaft cover structure 20 at leastpartially defines the particle collection chamber 34, as noted above.The particle collection chamber 34 extends circumferentially about theshaft 22 and is in fluid communication with the annular cavity 84. Theparticle collection chamber 34 is located upstream of the particledeflecting structure 90 and at least partially radially outwardly fromthe annular cavity 84. As will be described in detail herein, theparticle collection chamber 34 collects particles deflected from thefirst portion of cooling fluid by the particle deflecting structure 90.It is noted that some particles may flow directly into the particlecollection chamber 34, i.e., without being deflected by the particledeflecting structure 90, as a result of the particles moving radiallyoutwardly, as will be discussed herein.

Referring to FIGS. 1-3, the bypass passages 32 provide cooling fluid,including a second portion of cooling fluid from the cooling fluidchamber 50 to a metering structure 120, which metering structure 120provides the second portion of cooling fluid from the bypass passages 32into the turbine rim cavity 100.

The bypass passages 32 according to this aspect of the present inventioncomprise two types of passages. Specifically, a plurality of primarybypass passages 132 provide cooling fluid located in the shaft covercavity 108 to the metering structure 120, wherein at least a portion ofthe cooling fluid located in the shaft cover cavity 108 is from thecooling fluid chamber 50. Further, a plurality of secondary bypasspassages 134 provide cooling fluid located in the cooling fluid chamber50 directly to the metering structure 120.

As noted above, at least a portion of the cooling fluid in the shaftcover cavity 108 that flows to the metering structure 120 through theprimary bypass passages 132 comprises cooling fluid from the coolingfluid cavity 50. Specifically, cooling fluid flows from the coolingfluid cavity 50 through one or more cooling fluid ports 136 (see FIG. 1)formed in the forward end portion 24 of the shaft cover structure 20. Aportion of this cooling fluid leaks through the shaft seal assembly 28into the shaft cover cavity 108, and then flows to the meteringstructure 120 via the primary bypass passages 132.

Additional cooling fluid in the shaft cover cavity 108 may enter theshaft cover cavity 108 from the annular cavity 84 by leaking through thesecond sealing structure 106. It is noted that cooling fluid preferablydoes not leak from the shaft cover cavity 108 into the annular cavity84, as the pressure of the cooling fluid in the annular cavity 84 ispreferably as high as or higher than the pressure of the cooling fluidlocated within the shaft cover cavity 108.

The primary bypass passages 132 in the embodiment shown extend radiallyoutwardly and axially downstream from where they communicate with theshaft cover cavity 108 to a location L_(P) (see FIG. 2) and then extendgenerally axially downstream to the metering structure 120. The radiallyand axially extending sections of the primary bypass passages 132 do notcommunicate with the pre-swirl passages 60, such that the cooling fluidin the primary bypass passages 132 does not interact with the firstportion of cooling fluid flowing through the pre-swirl passages 60 tothe pre-swirl structure 30. This is accomplished in the embodiment shownby forming the primary bypass passages 132 through the shaft coverstructure 20 at different circumferential locations than the pre-swirlpassages 60.

The secondary bypass passages 134 extend generally axially downstreamfrom the cooling fluid chamber 50 to the metering structure 120, asshown in FIGS. 2 and 3. The secondary bypass passages 134 do notcommunicate with the pre-swirl passages 60, such that the cooling fluidin the secondary bypass passages 134 does not interact with the firstportion of cooling fluid flowing in the pre-swirl passages 60 to thepre-swirl structure 30. This is accomplished in the embodiment shown byforming the secondary bypass passages 134 through the shaft coverstructure 20 at different circumferential locations than the pre-swirlpassages 60. It is noted that the secondary bypass passages 134 are alsoformed through the shaft cover structure 20 at different circumferentiallocations than the primary bypass passages 132, such that the coolingfluid flowing in the secondary bypass passages 134 does not interactwith the cooling fluid flowing in the primary bypass passages 132.

According to an aspect of the invention, the ratio of primary bypasspassages 132 to secondary bypass passages 134 may be, for example, about3 to 1. According to the embodiment shown, the number of primary bypasspassages 132 is 18 and the number of secondary bypass passages 134 is 6.

The metering structure 120 according to the embodiment shown comprises aring-shaped metering member, shown in FIG. 5, which extendscircumferentially about the shaft 22 and is received in a correspondingcircumferentially extending slot 138 formed in the aft end portion 26 ofthe shaft cover structure 20, see FIGS. 2 and 3.

As shown in FIG. 5, the metering structure 120 comprises a plurality offirst and second flow passageways 140 and 142 formed therein. The flowpassageways 140 and 142 extend through the metering structure 120 andprovide fluid communication between the bypass passages 32 and theturbine rim cavity 100. Specifically, the first flow passageways 140provide fluid communication between outlets 132A of the primary bypasspassages 132 (see FIGS. 2, 3, and 5) and the turbine rim cavity 100,while the second flow passageways 142 provide fluid communicationbetween outlets 134A of the secondary bypass passages 134 (see FIGS. 2,3, and 5) and the turbine rim cavity 100. As shown in FIG. 5, the numberof first flow passageways 140 to the number of second flow passageways142 in the embodiment shown correspond to the number of primary bypasspassages 132 and secondary bypass passages 134, i.e., 18 first flowpassageways 140 and 6 second flow passageways 142 are provided in themetering structure 120 in the embodiment shown. However, it is notedthat extra bypass passages 32, i.e., primary and/or secondary bypasspassages 132, 134, may be formed in the shaft cover structure 20 in caseit is desirable to subsequently form additional flow passageways 140and/or 142 in the metering structure 120. This may be desirable for asituation where additional cooling fluid flow into the turbine rimcavity 100 is sought. If this is the case, additional flow passageways140 and/or 142 could be formed in the metering structure 120 at thelocations of the previously blocked outlets 132A, 134A of the respectivebypass passages 132, 134 to allow additional cooling fluid to flowthrough those bypass passages 132, 134 and corresponding flowpassageways 140, 142 into the turbine rim cavity 100.

Each flow passageway 140, 142 is formed in the metering structure 120 atan angle relative to the central axis C_(A) of the engine 10, such thatcooling fluid flowing out of each flow passageway 140, 142 has avelocity component in the direction tangential to the circumferentialdirection. According to the preferred embodiment, each flow passageway140, 142 is formed at an angle of at least about 70° relative to thecentral axis C_(A) of the engine 10.

Further, each flow passageway 140, 142 has a diameter D_(FP) (see FIG.5) that is no larger than about half the size of a diameter D_(BP) (seeFIG. 2) of a corresponding one of the bypass passages 132, 134. Thus, ifit is desirable to increase the amount of cooling fluid that passesthrough the metering structure 120 from the bypass passages 32 into theturbine rim cavity 100, the diameters D_(FP) of select ones or all ofthe flow passageways 140, 142 can be increased to accommodate theincreased flow volume. Alternatively, if it is desirable to decrease theamount of cooling fluid that passes through the metering structure 120from the bypass passages 32 into the turbine rim cavity 100, one or moreof the passageways 140, 142 could be blocked such that cooling fluiddoes not enter the turbine rim cavity 100 through the blockedpassageways 140, 142.

Since the diameters D_(BP) of the bypass passages 32 are larger than thediameters D_(FP) of the flow passageways 140, 142, the bypass passages32 can accommodate the additional flow volume without being altered. Itis noted that the diameters D_(BP) of the bypass passages 32 and thediameters D_(FP) of the flow passageways 140, 142 are sized so as toprovide a sufficient amount of cooling fluid into the turbine rim cavity100 from the flow passageways 140, 142 to adequately cool the firstblade disc structure 114 and the first lower stator support structure118 and to reduce or prevent hot combustion gas ingestion into theturbine rim cavity 100 from the hot gas flow path HG. That is, asufficient amount of cooling fluid is provided into the turbine rimcavity 100 to maintain the pressure within the turbine rim cavity 100 ata level wherein leakage of hot combustion gases from the hot gas flowpath HG into the turbine rim cavity 100 is substantially prevented.However, in the preferred embodiment, the diameters D_(BP) of the bypasspassages 32 and the diameters D_(FP) of the flow passageways 140, 142are sized so as to limit the amount of cooling fluid provided to theturbine rim cavity 100; hence, maintaining the pressure within theturbine rim cavity 100 below the pressure within the annular cavity 84and not providing more cooling fluid into the turbine rim cavity 100than is needed. Thus, any leakage between the turbine rim cavity 100 andthe annular cavity 84 through the first sealing structure 98 is from theannular cavity 84 into the turbine rim cavity 100. This is preferable,as cooling fluid leaking from the turbine rim cavity 100 into theannular cavity 84 could reduce the velocity component V_(TC) of thefirst portion of cooling fluid flowing into the bores 86 in the firstblade disc structure 114, which is undesirable.

During operation of the engine 10, compressed air from the compressorsection 11 is provided to the combustion section 12 and is burned withfuel to create hot working gases as discussed above. The hot workinggases from the combustion section 12 are directed into and through thetransition ducts 12A and are released into the turbine section 13. Theworking gases flow through the hot gas path HG in the turbine section 13where the working gases are expanded and cause the blades 14 and bladedisc structures to rotate to effect rotation of the rotor 16 and theshaft 22.

Cooling fluid, e.g., compressor bleed air that may be cooled in anexternal cooler, enters the cooling fluid chamber 50 via the coolingfluid feed tubes 52, see FIG. 1. A first portion of the cooling fluidflows to the pre-swirl structure 30 through the pre-swirl passages 60,wherein the first portion of cooling fluid flows through the flowpassage 68 of the pre-swirl structure 30.

As the first portion of cooling fluid passes through the flow passage 68of the pre-swirl structure 30, the swirl members 74 provide to thecooling fluid a velocity component V_(TC) in the direction tangential tothe circumferential direction, as discussed above. This tangentialvelocity component V_(TC) of the first portion of cooling fluid as thefirst portion of cooling fluid exits the flow passage outlet 72 is suchthat a swirl ratio, which is defined as the velocity component V_(TC) ofthe cooling fluid in the direction tangential to the circumferentialdirection to a velocity component of the shaft 22 in the directiontangential to the circumferential direction, is greater than one. In apreferred embodiment for the engine 10 illustrated herein, as thecooling fluid passes out of the pre-swirl structure 30, the swirl ratiois preferably between about 1.15 and about 1.25. It is noted that thedesired swirl ratio of the cooling fluid passing out of the pre-swirlstructure 30 may vary depending on the particular engine in which thepre-swirl structure 30 is employed. For example, for some types ofengines, this swirl ratio may be as high as about 3. In FIG. 6, swirlratios of the cooling fluid at relevant sections of the engine 10 areillustrated.

The cooling fluid passing out of the pre-swirl structure 30 enters theannular cavity 84, where the first portion of cooling fluid flowscircumferentially, i.e., due to passing through the pre-swirl structure30, and also flows axially downstream toward the bores 86 formed in thefirst blade disc structure 114. It is noted that the downstream flow ofthe cooling fluid is caused by the pressure in the internal coolingcircuits 14A₁ formed in the blades 14 being lower than both the pressureof the cooling fluid in the cooling fluid chamber 50 and the pressure ofthe cooling fluid in the annular cavity 84.

The axial flow of the first portion of cooling fluid through the annularcavity 84 is desirable to allow for particles to flow to the radiallyouter portion of the annular cavity 84, such that the particles can beremoved from the first portion of cooling fluid by the particleseparator 89. Specifically, as the first portion of cooling fluid flowscircumferentially in the annular cavity 84, solid particles, such asrust particles, sand, etc., which may be carried with the first portionof cooling fluid, flow radially outwardly to the radially outer portionof the annular cavity 84. This radially outer flow of the solidparticles is caused by centrifugal forces that act on the particles,which have more mass and therefore more momentum than the cooling fluidwith which the particles are flowing.

Since the solid particles are caused to flow to the radially outerportion of the annular cavity 84, some of the particles flow directlyinto the particle collection chamber 34. Other particles flow axiallythrough the annular cavity 84 and contact the radially inwardlyextending portion 94 of the particle deflecting structure 90. Uponcontacting the radially inwardly extending portion 94 of the particledeflecting structure 90, the particles are deflected thereby and flowaxially upstream along the slight radial slope of the axially extendingportion 96 of the particle deflecting structure 90 toward the particlecollection chamber 34. It is noted that the tendency for the particlesto flow upstream may be caused, at least in part, by the slight radialslope of the axially extending portion 96 and the centrifugal forcesacting on the particles that cause the particles to flow radiallyoutwardly, i.e., caused by their mass.

The majority of the solid particles deflected by the particle deflectingstructure 90 are collected in the particle collection chamber 34, wherethey can be removed therefrom, for example, during maintenance of theengine 10. However, it is noted that a small amount of the particles mayflow through the first sealing structure 98 into the turbine rim cavity100. It is believed that these particles may eventually pass into thehot gas flow path HG, where they may be burned off by the hot combustiongases or carried along the hot gas path HG with the combustion gases. Itis also noted that some small particles may not have enough mass to flowto the radially outer portion of the annular cavity 84. These smallparticles may flow with the cooling fluid into the bores 86 in the firstblade disc structure 114. However, most of the larger particles arebelieved to be separated and removed from the cooling fluid by theparticle separator 89.

It is noted that an axial flow distance A_(F) (see FIG. 6) of the firstportion of cooling fluid within the annular cavity 84 in the engine 10illustrated herein is greater than a radial flow distance R_(F) (seeFIG. 6) of the first portion of cooling fluid within the annular cavity84 as the first portion of cooling fluid flows from the flow passageoutlet 72 to the bores 86 formed in the first blade disc structure 114.In the engine 10 illustrated herein, the radial flow distance R_(F) ofthe first portion of cooling fluid within the annular cavity 84 is about⅔ of the axial flow distance A_(F) of the first portion of cooling fluidwithin the annular cavity 84, e.g., the axial flow distance A_(F) may beabout 97 mm, and the radial flow distance R_(F) may be about 62 mm.According to one embodiment, the axial flow distance A_(F) may be atleast about 50 mm, which distance is believed to allow for most of thesolid particles to be removed from the first portion of the coolingfluid by the particle separator 89. Specifically, since the particledeflecting structure 90 is located axially close to the bores 86, thefirst portion of cooling fluid swirls a sufficient amount in the annularcavity 84 to cause the majority of the solid particles to move to theradially outer portion of the annular cavity 84, such that the particlescan be separated from the first portion of the cooling fluid by theparticle separator 89, as discussed above. According to anotherembodiment, the axial flow distance A_(F) may be at least about 75 mm,such that more of the particles can be removed from the first portion ofcooling fluid.

As shown in FIG. 6, once the first portion of cooling fluid traversesthe axial flow distance A_(F) of the annular cavity 84 and solidparticles are removed by the particle separator 89, the cooling fluidflows into a free vortex portion 84A of the annular cavity 84, where thecooling fluid flows radially outwardly in the free vortex portion 84Atowards the bores 86 in the first blade disc structure 114. As the firstportion of cooling fluid flows radially outwardly into the bores 86, thevelocity component V_(TC) of the cooling fluid in the directiontangential to the circumferential direction decreases, due to a freevortex or inviscid behavior, such that the velocity component V_(TC) ofthe cooling fluid preferably becomes approximately equal to that of theshaft 22 and the rotor 16. That is, the swirl ratio just before thecooling fluid enters the bores 86 is about 1 (see FIG. 6). Thisreduction in the velocity component V_(TC) is caused by free vortexbehavior as a result of the angular momentum of the first portion ofcooling fluid dominating the angular momentum of the rotor drag in anear inviscid fashion. In this area, i.e., in the free vortex portion84A of the annular cavity 84, angular momentum of the rotor 16 isconstant.

The velocity component V_(TC) decrease of the first portion of coolingfluid causes a corresponding static pressure increase of the coolingfluid, which is obtained free of any transfer or work, i.e., of therotor 16 on the first portion of cooling fluid, and is non parasitic.The pressure of the cooling fluid is preferably increased to a pressurethat is greater than the pressure of the hot combustion gases flowingthrough the hot gas flow path HG due to both a free vortex staticpressure increase resulting from the decrease in the velocity componentV_(TC) and a forced vortex total pressure increase in the bores 86resulting from the rotation of the bores 86. Hence, hot gas ingestioninto the internal cooling circuits 14A₁ formed in the blades 14 issubstantially avoided. It is noted that it may be desirable for thepressure of the cooling fluid as it enters the bores 86 in the firstblade disc structure 114 to be equal to a preset value defined by theengine manufacturer for a given engine to ensure that the pressure ofthe cooling fluid entering the bores 86 is slightly greater than thepressure of the hot combustion gases flowing through the hot gas flowpath HG.

It is noted that, since the bores 86 extend radially outwardly as thecooling fluid passes therethrough, the cooling fluid is caused to moveat the same rotational speed as the first blade disc structure 114,i.e., such that the swirl ratio is equal to 1 as the cooling fluid flowswithin the bores 86. Since the first portion of cooling fluid and thefirst blade disc structure 114 include generally the same velocitycomponent in the direction tangential to the circumferential directionjust prior to the cooling fluid entering the bores 86, i.e. the swirlration is about 1 just prior to the cooling fluid entering the bores 86,the rotor 16 is not required to increase the velocity component V_(TC)of the cooling fluid up to that of the first blade disc structure 114.This is desirable, because if the velocity component V_(TC) of thecooling fluid were to be increased by the rotor 16, a correspondingpressure drop and temperature increase would result from the velocityincrease. The temperature increase would result in an increase in thetemperature of the first portion of cooling fluid flowing into the bores86. Such a temperature increase is undesirable, as it would adverselyaffect cooling of the blades 14 and the other structure to be cooledwithin the turbine section 13. Further, by decreasing or avoiding thepressure drop of the first portion of cooling fluid as it enters thebores 86, an increased pressure drop is achieved as the first portion ofcooling fluid passes through the pre-swirl structure 30. Thus, acorresponding velocity component V_(TC) increase of the cooling fluid,i.e., due to the pressure drop increase, is increased as the firstportion of cooling fluid passes through the pre-swirl structure 30.

Additionally, since the rotor 16 is not required to increase thevelocity component V_(TC) of the cooling fluid up to that of the firstblade disc structure 114 prior to the cooling fluid entering the bores86, the rotor 16 is not required to expend any work that would otherwisebe required to increase the velocity component V_(TC) of the coolingfluid up to the same velocity component as the first blade discstructure 114 as the cooling fluid enters the bores 86. Hence, workexpended to rotate the rotor/shaft is believed to be conserved, whichincreases the efficiency and output of the engine 10. Further, theconservation of the rotor work may result in an increase in the rotatingvelocity of the rotor/shaft and/or a reduction in the amount of fuelrequired to rotate the rotor/shaft. It is noted that some work must bedone by the rotor 16 to maintain the swirl ratio at 1 as the firstportion of cooling fluid flows radially outwardly in the bores 86.However, the work saved by the rotor 16 not being required to increasethe velocity component V_(TC) of the cooling fluid up to the samevelocity component as the first blade disc structure 114 as the coolingfluid enters the bores 86 results in the benefits discussed above.

It is also noted that, this conserving of rotor work is also believed toavoid an increase in the temperature of the cooling fluid that wouldotherwise be associated with the rotor 16 expending the work to increasethe velocity component V_(TC) of the cooling fluid up to the samevelocity component as the first blade disc structure 114 as the coolingfluid enters the bores 86. That is, if the rotor 16 were required toincrease the velocity component V_(TC) of the cooling fluid as thecooling fluid enters the bores 86, the work done by the rotor 16 wouldheat up the cooling fluid entering the bores 86, i.e., caused by acombination of Euler work and/or windage forces or friction forces.However, since this work of the rotor 16 to increase the velocitycomponent V_(TC) of the cooling fluid is not needed, the temperatureincrease of the cooling fluid associated with the work is avoided.Hence, the cooling fluid flowing into the cooling fluid chamber 50 neednot be as cool as in a situation where the cooling fluid would otherwisebe heated by the Euler work and/or windage forces or friction forces.

Moreover, since the majority of the solid particles in the first portionof cooling fluid are deflected by the particle deflecting structure 90and captured in the particle collection chamber 34, particle flow intothe bores 86 and into the internal cooling circuits 14A₁ formed in theblades 14 downstream from the bores 86 is reduced. Reducing the numberof particles and the sizes of the particles that enter bores 86 and theinternal cooling circuits 14A₁ formed in the blades 14 is believed toimprove cooling to the blades 14, as particles (especially largeparticles) can clog or otherwise block cooling passages and/or coolingholes that deliver the cooling fluid to the blades 14 and otherstructure to be cooled by the cooling fluid. Since these coolingpassages and/or cooling holes are not likely to be blocked by particles,i.e., since the particles are separated from the cooling fluid by theparticle separator 89, these cooling passages and/or cooling holes maybe designed to have smaller diameters that in prior art engines. This isbecause diameters of cooling passages and/or cooling holes in prior artengines are typically designed so as to tolerate particles to beconveyed therethrough along with the cooling fluid. If the coolingpassages and/or cooling holes can be designed to have smaller diameters,a lesser amount of cooling air may be supplied from the cooling fluidchamber 50 while still providing adequate cooling to the components tobe cooled in the turbine section 13.

A second portion of cooling fluid flows through the bypass passages 32to the metering structure 120, which conveys the second portion ofcooling fluid into the turbine rim cavity 100. As discussed above, someof the second portion of cooling fluid passes to the metering structure120 through the primary bypass passages 132, and some of the secondportion of cooling fluid flows to the metering structure 120 through thesecondary bypass passages 134. As noted above, the second portion ofcooling fluid flowing to the metering structure 120 does not interactwith the first portion of cooling fluid flowing through the pre-swirlpassages 60 to the pre-swirl structure 30.

Since the flow passageways 140, 142 formed in the metering structure 120are angled relative to horizontal, the second portion of cooling fluidflowing into the turbine rim cavity 100 from the metering structure 120includes a velocity component in the direction tangential to thecircumferential direction in the same direction as the rotor 16 and theshaft 22 rotate. Thus, the second portion of cooling fluid entering theturbine rim cavity 100 from the metering structure 120 does not slowdown the rotor 16, i.e., due to windage forces, which is believed tofurther increase the efficiency of the engine 10.

Referring now to FIG. 7, a portion of a gas turbine engine 210 accordingto another embodiment of the invention is shown. The engine 210 includesa central axis C_(A1) defining an axial direction of the engine 210. Theengine 210 comprises a conventional compressor section 211, a combustionsection 212, and a turbine section 213 as discussed above with referenceto the engine 10. A plurality blade disc structures, including a firstblade disc structure 214, are positioned adjacent to one another in theaxial direction so as to define a rotor 216, and a plurality of vaneassemblies, including a first row vane assembly 218, are positionedadjacent to one another in the axial direction between respective bladedisc structures, as discussed above.

As shown in FIG. 7, a shaft cover structure 220 surrounds a portion of ashaft 222, which shaft 222 is coupled to the rotor 216 for rotation withthe rotor 216. The shaft cover structure 220 according to thisembodiment comprises an outer shaft cover 224, also referred to hereinwith respect to FIGS. 1-6 as an “outer cover”, and an inner shaft cover226, also referred to herein with respect to FIGS. 1-6 as a “shaft coverstructure”. It is noted that the shaft cover structure 220 does notrotate with the shaft 222 during operation of the engine 210.

The outer shaft cover 224 is located radially outwardly from the innershaft cover 226 and cooperates with the inner shaft cover 226 to definea cooling fluid chamber 228 therebetween. The cooling fluid chamber 228receives cooling fluid from a supply of cooling fluid as discussed abovewith respect to FIGS. 1-6. The outer shaft cover 224 is structurallysupported by a main engine casing (not shown) via a plurality of struts(not shown) extending from the main engine casing to the outer shaftcover 224. The outer shaft cover 224 comprises a generally cylindricalmember having a forward end portion 230 and an opposed aft end portion232.

The inner shaft cover 226 comprises a generally cylindrical memberhaving a forward end portion 234 and an opposed aft end portion 236. Theinner shaft cover 226 is structurally supported by the outer shaft cover224 via a first seal structure 238 located adjacent to the forward endportions 230 and 234 of the outer and inner shaft covers 224 and 226.The first seal structure 238 also creates a substantially fluid tightseal between the forward end portions 230 and 234 of the outer and innershaft covers 224 and 226. Second seal structure 240, such as, forexample, a dog bone seal or diaphragm seal, is disposed between the aftend portion 232 of the outer shaft cover 224 and the aft end portion 236of the inner shaft cover 226 for creating a substantially fluid tightseal therebetween.

As shown in FIG. 7, an air separator structure 242 is located betweenthe shaft 222 and the inner shaft cover 226. The air separator structure242 comprises a generally cylindrical member and is coupled to androtates with the shaft 222 during operation of the engine 210. The airseparator structure 242 includes a first axially extending portion 242A,a second axially extending portion 242 downstream from the first axiallyextending portion 242A, and an air separator portion 242C downstreamfrom the second axially extending portion 242B. A plurality of spanningmembers 246 (one shown in FIG. 7) extend between the first and secondaxially extending portions 242A and 242B, which spanning members 246define a plurality of openings 248 therebetween, which openings 248 willbe discussed further below. The spanning members 246 provide structuralsupport for the second axially extending portion 242B and the airseparator portion 242C via the first axially extending portion 242A,which first axially extending portion 242A is coupled to the shaft 222at the location L_(S).

Referring additionally to FIG. 8, a first portion of cooling fluidsupplied by the cooling fluid chamber 228 flows radially inwardlythrough a series of inlet openings 250 formed in the inner shaft cover226. The inlet openings 250 are defined by a plurality ofcircumferentially spaced apart inner shaft cover struts 252 that extendaxially between a first axially extending portion 226A of the innershaft cover 226 and a second axially extending portion 226B of the innershaft cover 226 downstream from the first axially extending portion 226A(FIG. 7). The first portion of cooling fluid passes through the inletopenings 250 to a pre-swirl structure 256 according to this aspect ofthe invention.

As shown in FIG. 7, the pre-swirl structure 256 includes a forward wallstructure 258 that extends circumferentially about the shaft 222 and iscoupled to the first axially extending portion 226A of inner shaft cover226. The pre-swirl structure 256 also includes an aft wall structure 260axially spaced from the forward wall structure 258. The aft wallstructure 260 extends circumferentially about the shaft 222 and iscoupled to the second axially extending portion 226B of inner shaftcover 226. The forward and aft wall structures 258 and 260 define anannular flow passage 262 therebetween, which flow passage 262 includesan inlet 264 and an outlet 266 (see also FIGS. 8 and 8A), through whichthe first portion of cooling fluid passes after entering the pre-swirlstructure 256 from the cooling fluid chamber 228, as will be describedherein.

As shown in FIGS. 7, 8, and 8A a plurality of swirl members 268 extendin the flow passage 262. The swirl members 268 span between the forwardand aft wall structures 258, 260. As shown in FIG. 8A, the swirl members268 each include opposed first and second sidewalls 270, 272, a leadingedge 274 proximate to the flow passage inlet 264, and a trailing edge276 proximate to the flow passage outlet 266. In a preferred embodiment,the leading edges 274 of the swirl members 268 are circumferentiallyaligned with respective ones of the inner shaft cover struts 252 suchthat the inner shaft cover struts 252 do not block cooling fluidattempting to pass to the pre-swirl structure 256. That is, since theleading edges 274 of the swirl members 268 are circumferentially alignedwith the inner shaft cover struts 252, a direct radial path is providedthrough the inlet openings 250 for the first portion of cooling fluid toflow from the cooling fluid chamber 228 to the pre-swirl structure 256.

The leading edge 274 of each of the swirl members 268 is offset from thetrailing edge 276 in a circumferential direction, as shown in FIGS. 8and 8A. Thus, a flow direction of the first portion of cooling fluidflowing through the flow passage 262 is altered by the swirl members268, such that the first portion of cooling fluid exiting the flowpassage outlet 266 has a velocity vector V₁ (see FIG. 8A) with avelocity component V_(TC1) in a direction tangent to the circumferentialdirection, and a radial velocity component V_(R) as the first portion ofcooling fluid flows out of the flow passage outlet 266. An angle Ωbetween the velocity vector V₁ and its velocity component V_(R) may bebetween about 75° and about 85°. It is noted that the velocity componentV_(TC1) of the first portion of cooling fluid exiting the flow passageoutlet 266 in the direction tangent to the circumferential direction ispreferably substantially the same as a velocity component of the shaft222 and the rotor 216 in the direction tangent to the circumferentialdirection during operation of the engine 210.

Referring to FIG. 8A, in a preferred embodiment, the swirl members 268are configured such that the cooling fluid exiting the flow passageoutlet 266 flows or moves in a direction D₂ at an angle Ω_(D) of fromabout 75° to about 85° relative to a radial axis R_(A) (see FIGS. 7 and8) of the engine 210. Such a flow direction D₂ of the cooling fluid canbe effected by forming the trailing edges 276 of the swirl members 268so that they extend at an angle Ω_(SM) of from about 75° to about 85°relative to the radial axis R_(A) of the engine 210.

Further, as shown in FIG. 8A, the swirl members 268 in the preferredembodiment are circumferentially spaced apart from one another so as toallow a desired amount of cooling fluid through the flow passage 262 toadequately cool structure to be cooled in the turbine section 213 of theengine 210, as will be discussed herein. The narrowest spacing S_(P1)between the trailing edge 276 of one swirl member 268 and the secondsidewall 272 of an adjacent swirl member 268, which spacing S_(P1) mayalso be referred to as the throat section between the swirl members 268,is also preferably configured to obtain a desired pressure drop, i.e.,caused by a Venturi effect effected by the converging sidewalls 270 and272 of the swirl members 268, and to cause a corresponding velocityincrease as the cooling fluid flows through the flow passage 262.According to one embodiment, the narrowest spacing S_(P1) between thefirst sidewall 270 at the trailing edge 276 of one swirl member 268 andthe second sidewall 272 of the adjacent swirl member 268 may be about 10mm, but may vary depending upon the particular configuration of theengine 210. An axial length L₁ (see FIG. 7) of each of the swirl members268 according to an exemplary embodiment of the invention may be about15-25 mm and a chordal height H₁ (see FIG. 8A) of each of the swirlmembers 268 according to an exemplary embodiment of the invention may beabout 60-105 mm.

Referring back to FIG. 7, the first portion of cooling fluid exits theflow passage 262, passes through the openings 248 in the air separatorstructure 242, and enters a flow path 280 located between the shaft 222and the shaft cover structure 220, i.e., between the air separatorstructure 242 and the shaft 222 in the embodiment shown. The flow path280 extends generally in the axial direction between the air separatorstructure 242 and the shaft 222 and provides fluid communication betweenthe pre-swirl structure 256 and a plurality of bores 282 formed in thefirst blade disc structure 214.

First ones 282A of the bores 282 in the first blade disc structure 214extend radially outwardly through the first blade disc structure 214 toprovide a first allocation of the first portion of cooling fluid toblades of the first blade disc structure 214, which blades weredescribed above with respect to FIGS. 1-6. Second ones 282B of the bores282 are provided as a pathway for a second allocation of the firstportion of cooling fluid to remaining blade disc structures in theturbine section 213 of the engine 210.

As shown in FIG. 7, a plurality of bypass passages 290 (one shown inFIG. 7) provide a second portion of cooling fluid, which may include asmall amount of the first portion of cooling fluid (as will be describedherein) to a metering structure 292 located at exit openings 290A of thebypass passages 290 at an end 296 of the inner shaft cover 226. Themetering structure 292 provides the second portion of cooling fluid fromthe bypass passages 290 into a turbine rim cavity 294, which turbine rimcavity 294 was described above with respect to FIGS. 1-6.

The bypass passages 290 according to this aspect of the inventioncomprise inlet openings 298 formed in a radially inner surface 300 ofthe first axially extending portion 226A of the inner shaft cover 226.The bypass passages 290 extend radially outwardly and axially downstreamfrom the inlet openings 298 through the inner shaft cover 226 to alocation L_(P1) and then extend generally axially downstream through theinner shaft cover 226 to the metering structure 292 located at the exitopenings 290A.

The bypass passages 290 do not communicate with the inlet openings 250in the inner shaft cover 226 or with the flow passage 262 or the flowpath 280, such that the second portion of cooling fluid in the bypasspassages 290 does not interact with the first portion of cooling fluidflowing into and through pre-swirl structure 256 and into the flow path280. This is accomplished in the embodiment shown by forming a portionof the bypass passages 290 through the inner shaft cover struts 252 (seealso FIGS. 8 and 8A). It is noted that the number of inner shaft coverstruts 252 having bypass passages 290 passing therethrough may varydepending on the amount of cooling fluid that is desirable to beprovided into the turbine rim cavity 294. However, at least some of theinner shaft cover struts 252 preferably do not include bypass passages290 passing therethrough, as shown in FIG. 7, so as to preserve thestructural rigidity of the inner shaft cover 226.

The metering structure 292 according to this aspect of the invention maycomprise a ring-shaped metering member, as discussed above with respectto FIGS. 1-6 and as shown in FIG. 5. The metering structure 292comprises a plurality flow passageways 306 formed therein, which flowpassageways 306 extend through the metering structure 292 and providefluid communication between the bypass passages 290 and the turbine rimcavity 294. As discussed above with reference to FIGS. 1-6, each flowpassageway 306 is preferably formed in the metering structure 292 at anangle relative to the central axis C_(A1) of the engine 210, such thatcooling fluid flowing out of each flow passageway 306 has a velocitycomponent in the direction tangential to the circumferential direction.According to the preferred embodiment, each flow passageway 306 isformed at an angle of at least about 70° relative to the central axisC_(A1) of the engine 210.

Remaining structure of the metering structure 292 is substantiallysimilar to the metering structure 120 described above with reference toFIGS. 1-6, with the exception of the metering structure 292 according tothis embodiment only comprising one type of flow passageway 306 sinceonly one type of bypass passage 290 is provided in this embodiment.

As shown in FIG. 7, the forward end portion 234 of the inner shaft cover226 includes a plurality of cooling fluid ports 308 formed therein (onlyone cooling fluid port 308 is shown in FIG. 7). A main amount of thesecond portion of cooling fluid passes through the cooling fluid ports308 on its way to the bypass passages 290, as will be discussed herein.Further, a third portion of cooling fluid flows through the coolingfluid ports 308. The third portion of cooling fluid is provided to achamber 310 in communication with the compressor section 211 of theengine 210 to provide cooling to structure to be cooled in thecompressor section 211, such as, for example, conventional compressordiscs (not shown).

The main amount of the second portion of cooling fluid passes through aseal member 312 located radially between the first axially extendingportion 242A of the air separator structure 242 and the first axiallyending portion 226A of the inner shaft cover 226 and located axiallybetween an end surface 314 of the inner shaft cover 226 and the bypasspassages 290. The seal member 312 may comprise for example, a rotatingstructure, such as a knife edge seal, coupled to the air separatorstructure 242, which may be in combination with a non-rotating sealstructure, such as a honeycomb seal or an abradable material, coupled tothe inner shaft cover 226. Other suitable exemplary types of first sealmembers include leaf seals, brush seals, and non-contacting fin seals.While the seal member 312 prevents substantial leakage between the firstaxially extending portion 242A of the air separator structure 242 andthe first axially ending portion 226A of the inner shaft cover 226, themain amount of the second portion of cooling fluid passes through thecooling fluid ports 308 and through the seal member 312 on its way tothe bypass passages 290 since a pressure at the bypass passages 290 isless than a pressure in the cooling fluid chamber 228.

As noted above, the second portion of cooling fluid may include a smallamount of the first portion of cooling fluid. Specifically, a smallamount of the first portion of cooling fluid may leak through a firstsealing structure 316 located radially between the first axiallyextending portion 242A of the air separator structure 242 and the firstaxially ending portion 226A of the inner shaft cover 226 and locatedaxially between the bypass passages 290 and the pre-swirl structure 256.The first sealing structure 316 may comprise for example, a rotatingstructure, such as a knife edge seal, coupled to the air separatorstructure 242, which may be in combination with a non-rotating sealstructure, such as a honeycomb seal or an abradable material, coupled tothe inner shaft cover 226. Other suitable exemplary types of firstsealing structures include leaf seals, brush seals, and non-contactingfin seals. While the first sealing structure 316 prevents a substantialamount of cooling fluid exiting the pre-swirl structure 256 via the flowpassage outlet 266 from entering the bypass passages 290, a small amountof the first portion of cooling fluid passing from the pre-swirlstructure 256 into the flow path 280 may leak through the first sealingstructure 316 since the pressure at the bypass passages 290 is less thanthe pressure of the first portion of cooling fluid as it exits thepre-swirl structure 256.

Referring still to FIG. 7, a second sealing structure 318 is locatedradially between the second axially extending portion 242B of the airseparator structure 242 and the second axially extending portion 226B ofthe inner shaft cover 226 and is located axially between the pre-swirlstructure 256 and the turbine rim cavity 294. The second sealingstructure 318 may comprise for example, a rotating structure, such as aknife edge seal, coupled to the air separator structure 242, which maybe in combination with a non-rotating seal structure, such as ahoneycomb seal or an abradable material, coupled to the inner shaftcover 226. Other suitable exemplary types of second sealing structuresinclude leaf seals, brush seals, and non-contacting fin seals. While thesecond sealing structure 318 prevents a substantial amount of coolingfluid exiting the pre-swirl structure 256 via the flow passage outlet266 from entering the turbine rim cavity 294, a small amount of thefirst portion of cooling fluid may leak through the second sealingstructure 318 since the pressure at the turbine rim cavity 294 is lessthan the pressure of the first portion of cooling fluid as it exits thepre-swirl structure 256.

During operation of the engine 210 the first portion of the coolingfluid flows to the pre-swirl structure 256 through the inlet openings250 in the inner shaft cover 226. The first portion of cooling fluidpasses through the flow passage 262 of the pre-swirl structure 256 andthe swirl members 268 provide a velocity component V^(TC1) to thecooling fluid in the direction tangential to the circumferentialdirection, as discussed above.

The first portion of cooling fluid passing out of the pre-swirlstructure 256 passes through the openings 248 and enters the flow path280, where the first portion of cooling fluid flows circumferentially,i.e., due to passing through the pre-swirl structure 256, and also flowsaxially downstream toward the bores 282 formed in the first blade discstructure 214. The axial flow of the first portion of cooling fluidthrough the flow path 280 is desirable to allow for the velocitycomponent V_(TC1) of the first portion of cooling fluid in thecircumferential direction to substantially match that of the shaft 222and the air separator structure 242, which is coupled to the shaft 222.

Once the first portion of cooling fluid traverses an axial flow distanceA_(F1) of the flow path 280, the second allocation of the first portionof cooling fluid enters the second ones 282B of the bores 282 and isprovided to remaining blade disc structures in the turbine section 213of the engine 210. The first allocation of the first portion of coolingfluid flows into a free vortex portion 320 of an annular cavity 322, seeFIG. 7. Details in connection with the flow of the first allocation ofthe cooling fluid in the free vortex portion 320 of the annular cavity322 are disclosed above with respect to FIGS. 1-6. It is noted that theannular cavity 322 in the embodiment shown in FIG. 7 is separated fromthe second portion of cooling fluid on its way to the turbine rim cavity294 by the air separator portion 242C of the air separator structure242.

Also during operation of the engine 210, the second portion of coolingfluid flows through the bypass passages 290 to the metering structure292, which metering structure 292 conveys the second portion of coolingfluid into the turbine rim cavity 294, as discussed above. Further, thethird portion of cooling fluid is provided into the chamber 310 to coolthe structure to be cooled in the compressor section 211 of the engine210.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A gas turbine engine having a central axis defining an axialdirection comprising: a supply of cooling fluid; a rotatable shaftextending in the axial direction of the engine; shaft cover structuredisposed about said shaft such that a flow path extends in the axialdirection between said shaft and said shaft cover structure; pre-swirlstructure coupled to said shaft cover structure and located radiallybetween said supply of cooling fluid and said flow path, said pre-swirlstructure extending in a circumferential direction about said shaft,said pre-swirl structure comprising: forward wall structure; aft wallstructure spaced in the axial direction from said forward wallstructure, said forward and aft wall structures defining a flow passagetherebetween, said flow passage including an inlet in communication withsaid supply of cooling fluid and an outlet in communication with saidflow path, said flow passage supplying a first portion of cooling fluidfrom said supply of cooling fluid to said flow path; and a plurality ofswirl members in said flow passage extending between said forward andaft wall structures, said swirl members each including a leading edgeand a trailing edge spaced from said leading edge in a radial direction,wherein said trailing edge is offset from said leading edge in thecircumferential direction; wherein a flow direction of the first portionof cooling fluid passing through said flow passage is altered by saidswirl members such that the first portion of cooling fluid has avelocity component in a direction tangential to the circumferentialdirection when the first portion of cooling fluid enters said flowpassage; and at least one bypass passage defined through said shaftcover structure, said at least one bypass passage receiving a secondportion of cooling fluid from said supply of cooling fluid, said atleast one bypass passage including an exit opening at an end of saidshaft cover structure supplying the second portion of cooling fluid to aturbine rim cavity associated with a first row vane assembly to preventhot gas ingestion into the turbine rim cavity from a hot gas flow pathassociated with a turbine section of the engine.
 2. The gas turbineengine according to claim 1, further comprising an air separatorstructure between said shaft and said shaft cover structure and having aportion extending axially from said pre-swirl structure to a locationadjacent to a blade disc structure coupled to said shaft, said airseparator structure and said shaft cooperating to define said flow paththerebetween.
 3. The gas turbine engine according to claim 2, whereinsaid air separator structure comprises a plurality of openings thereinadjacent to said outlet of said pre-swirl structure, said openingspermitting the first portion of cooling fluid to pass from saidpre-swirl structure into said flow path.
 4. The gas turbine engineaccording to claim 2, further comprising sealing structure downstreamfrom said pre-swirl structure and located between said air separatorstructure and said shaft cover structure, said sealing structurelimiting leakage between said outlet of said flow passage and a turbinerim cavity associated with a first row vane assembly.
 5. The gas turbineengine according to claim 4, wherein said pre-swirl structure and saidshaft cover structure do not rotate with said shaft and said airseparator structure rotates with said shaft during operation of the gasturbine engine.
 6. The gas turbine engine according to claim 1, furthercomprising blade disc structure coupled to said shaft at a locationaxially downstream from said pre-swirl structure, said blade discstructure having at least one bore formed therein, said at least onebore receiving cooling fluid from said flow path and delivering thecooling fluid from said flow path to structure to be cooled within aturbine section of the engine.
 7. The gas turbine engine according toclaim 1, wherein said swirl members are configured such that the coolingfluid exiting said flow passage flows at an angle of from about 75° toabout 85° relative to a radial axis of the gas turbine engine transverseto the central axis.
 8. The gas turbine engine according to claim 1,wherein said swirl members are arranged such that a spacing between afirst sidewall at said trailing edge of each said swirl member and asecond sidewall of an adjacent swirl member causes a Venturi effect asthe cooling fluid flows through said flow passage, the Venturi effectresulting in a pressure drop and a velocity increase of the coolingfluid flowing through said flow passage.
 9. The gas turbine engineaccording to claim 1, wherein: said shaft cover structure comprisesinner and outer shaft covers, said outer shaft cover structurallysupported by an engine casing and providing structural support for saidinner shaft cover; said supply of cooling fluid comprises a chamberlocated between said inner and outer shaft covers; and said pre-swirlstructure is coupled to said inner shaft cover.
 10. The gas turbineengine according to claim 1, wherein said shaft cover structurecomprises a plurality of struts spaced apart from each other in thecircumferential direction, said struts defining inlet openings to saidpre-swirl structure therebetween, wherein at least a portion of eachsaid bypass passage extends through a corresponding one of said struts.11. The gas turbine engine according to claim 1, further comprising ametering structure associated with an outlet of each said bypasspassage, said metering structure comprising at least one flow passagewayformed therein for permitting the second portion of cooling fluid ineach said bypass passage to pass into the turbine rim cavity.
 12. Thegas turbine engine according to claim 11, wherein each said flowpassageway is formed in said metering structure at an angle such thatthe second portion of cooling fluid flowing out of each said flowpassageway has a velocity component in the direction tangential to thecircumferential direction
 13. A gas turbine engine having a central axisdefining an axial direction comprising: a supply of cooling fluid; arotatable shaft extending in the axial direction of the engine; shaftcover structure disposed about said shaft such that a flow path extendsin the axial direction between said shaft and said shaft coverstructure; pre-swirl structure coupled to said shaft cover structure andlocated radially between said supply of cooling fluid and said flowpath, said pre-swirl structure extending in a circumferential directionabout said shaft, said pre-swirl structure comprising: a flow passageincluding an inlet in communication with said supply of cooling fluidand an outlet in communication with said flow path, said flow passagesupplying a first portion of cooling fluid from said supply of coolingfluid to said flow path; and a plurality of swirl members in said flowpassage, said swirl members each including a leading edge and a trailingedge spaced from said leading edge in a radial direction, wherein saidtrailing edge is offset from said leading edge in the circumferentialdirection; wherein a flow direction of the first portion of coolingfluid passing through said flow passage is altered by said swirl memberssuch that the first portion of cooling fluid has a velocity component ina direction tangential to the circumferential direction when the coolingfluid enters said flow passage; a plurality of bypass passagesassociated with said shaft cover structure, said bypass passagesreceiving a second portion of cooling fluid from said supply of coolingfluid and supplying the second portion of cooling fluid to a turbine rimcavity associated with a first row vane assembly to prevent hot gasingestion into the turbine rim cavity from a hot gas flow pathassociated with a turbine section of the engine; and a meteringstructure associated with an outlet of each said bypass passage, saidmetering structure comprising a plurality of flow passageways formedtherein for permitting the second portion of cooling fluid in saidbypass passages to pass into the turbine rim cavity.
 14. The gas turbineengine according to claim 13, wherein at least one of said flowpassageways is formed in said metering structure at an angle such thatthe second portion of cooling fluid flowing out of said flow passagewayshas a velocity component in the direction tangential to thecircumferential direction.
 15. The gas turbine engine according to claim13, wherein said pre-swirl structure further comprises: forward wallstructure; and aft wall structure spaced in the axial direction fromsaid forward wall structure, said forward and aft wall structuresdefining said flow passage therebetween and said swirl members extendingfrom said forward wall structure to said aft wall structure.
 16. The gasturbine engine according to claim 13, wherein: said shaft coverstructure comprises inner and outer shaft covers, said outer shaft coverstructurally supported by an engine casing and providing structuralsupport for said inner shaft cover; said supply of cooling fluidcomprises a chamber located between said inner and outer shaft covers;said pre-swirl structure is coupled to said inner shaft cover; and saidbypass passages are associated with said inner shaft cover.
 17. The gasturbine engine according to claim 13, further comprising: an airseparator structure between said shaft and said shaft cover structure,said air separator structure and said shaft cooperating to define saidflow path therebetween; first sealing structure located radially betweena first axially extending portion of said air separator structure andsaid shaft cover structure and located axially between said bypasspassages and said pre-swirl structure, said first sealing structurelimiting leakage between said bypass passages and said outlet of saidflow passage; and second sealing structure located radially between asecond axially extending portion of said air separator structure andsaid shaft cover structure and located axially between said pre-swirlstructure and said turbine rim cavity, said second sealing structurelimiting leakage between said outlet of said flow passage and saidturbine rim cavity.
 18. The gas turbine engine according to claim 13,further comprising blade disc structure coupled to said shaft at alocation axially downstream from said pre-swirl structure, said bladedisc structure having at least one bore formed therein, said at leastone bore receiving the first portion of cooling fluid from said flowpath and delivering the first portion of cooling fluid to structure tobe cooled within the turbine section of the engine.
 19. The gas turbineengine according to claim 13, wherein said shaft cover structurecomprises a plurality of struts spaced apart from each other in thecircumferential direction, said struts defining inlet openings to saidpre-swirl structure therebetween, wherein at least a portion of eachsaid bypass passage extends through a corresponding one of said struts.20. The gas turbine engine according to claim 13, wherein said shaftcover structure comprises at least one cooling fluid port formed thereinfor permitting cooling fluid to flow into a chamber in communicationwith a compressor section of the engine for cooling structure to becooled in the compressor section.